The present invention relates generally to a connection structure making an electric connection between a head disk assembly and a printed board in a rotating disk storage device such as a magnetic disk drive, an optical magnetic disk drive, or the like. More particularly, the present invention relates to a connection structure making use of a flexible printed circuit board therefor and a rotating disk storage device adopting the connection structure.
A magnetic disk device generally includes a head disk assembly (hereinafter referred to as the HDA) and a printed board mounted on the HDA. The HDA is constructed so as to hermetically enclose a magnetic disk, a head suspension assembly, an actuator assembly, a spindle motor, an electronic component, and the like in a clean air environment using a disk enclosure. The printed board is mounted with an electronic component controlling an operation of, and data transfer for, the magnetic disk device. A flexible cable is provided inside the disk enclosure for making an electric connection between internal component parts housed in the disk enclosure and the printed board.
The flexible cable, also called a flexible printed circuit board, a flex cable, or the like, is provided with a plurality of conductors sandwiched between flexible sheets, each of the plurality of conductors being insulated from each other. The flexible cable is hereinafter referred to as an FPC (flexible printed circuit) in this specification. The following is described in the abstract of Japanese Patent Laid-Open No. 2000-331471 with reference to FIG. 7. That is, “an end portion 8a of an FPC 8 is extracted to an outside of a housing through an opening 15 provided in a base 2. The FPC 8 is pressed tightly up against a bottom surface 3 of the base 2 by way of double-sided adhesive tape 17. A closure seal 16 is then placed over the FPC 8 to plug the opening 15.” In addition, the following is described in that patent document with reference to FIG. 5. That is, “a first end portion 8a of the FPC 8 is extracted to the outside of the housing 1 through the opening 15. A control printed board 1 is mounted on the back of the base 2. The first end portion 8a is connected to a connector 18 mounted on a control printed board 9. This allows signals to be transferred between an inside of the housing 1 and a controller mounted on the control printed circuit 9.” FIG. 5 shows a state in which an electric connection is made by the connector 18 that sandwiches the end portion 8a of the FPC.
The following is described in Japanese Patent Laid-Open No. 2000-243076. That is, “in an example shown in FIG. 3, a terminal 4 of a connection portion of a flex cable 3 and a connector 12 shown in FIG. 2 are inserted in a groove portion 2 of a device main body 1 shown in FIG. 1. A terminal 13 of the connector 12 is thereby joined to the terminal 4 of the connection portion of the flex cable 3. At this time, guides 14-1 and 14-2 of the connector 12 are respectively fitted into guide grooves 7-1 and 7-2 of the device main body 1. This correctly positions the terminal 13 of the connector 2 relative to the terminal 4 of the connection portion of the flex cable 3. When the two parts are pressed into an inside of the groove portion 2, a spring of the terminal 13 of the connector 12 causes the terminal 13 of the connector 12 to be pressed against, and joined to, the terminal 4 of the flex cable 3. At this time, tolerances among a width W1 in a short side direction of an opening in the groove portion 2, a width W2 in a short side direction of the connector 12, and a thickness T of the connection portion of the flex cable 3 are controlled so as to fall within a movable range of the spring of the terminal 13 of the connector 12. This maintains a joint between the respective contact points of the terminals 4 and 13.”
The method of Japanese Patent Laid-open No. 2000-331471 described above involves the increased number of assembly processes, since it is necessary to sandwich the end portion 8a of the FPC with the connector 18 after the control printed board 7 has been mounted to the housing 1. According to the method of Japanese Patent Laid-open No. 2000-243076 described above, it is necessary to control the mutual dimensional tolerances among the width W1 in the short side direction of the opening in the groove portion 2, the width W2 in the short side direction of the connector 12, and the thickness T of the connection portion of the flex cable 3 so that the tolerances fall within the movable range of the spring of the terminal 13 of the connector 12.
With the recent trend in magnetic disk drives toward an even smaller body, the movable range of the spring of the connector terminal are becoming smaller and smaller. It has therefore become difficult to manufacture magnetic disk drives, while achieving close dimensional tolerances. In the example shown in FIG. 3 of the second patent document described above, there are involved a number of dimensions to be controlled. The dimensions to be controlled include: the width of the groove portion and the position of the groove portion relative to the device main body; the size of the connector and the position of the connector on the circuit board; the position of connection between the device and the circuit board; and the movable range of the spring of the terminal. If any of these dimensions falls outside a predetermined range of dimensional tolerances, a predetermined pressure cannot be obtained, resulting in a contact failure occurring at the terminal.